Currently, a refrigeration and air-conditioning system may include a plurality of compressors, and the compressors form a compressor system. In the compressor system, oil amount in a specific compressor may be insufficient if respective oil amounts in the compressors are not in balance, thereby shortening life cycle of the specific compressor and affecting stability of the compressor system. To avoid this problem, some oil balancing method is generally adopted to enable the oil amount in each of the compressors in the compressor system to stay in an optimal state.
However, the conventional oil-balancing method cannot timely achieve oil balance between the compressors in the compressor system in real time, it is thus common that a compressor is severely starved of oil, and the compressor which is starved of the oil has to be stopped in order to realize oil returning. As a result, the compressors may be frequently started and stopped.